A grimoire is defined as a book of spells and incantations used for calling forth spirits. The word “grimoire” is related to the word “grammar,” which pertains to the rules and the relationships of language. Derived from the Middle English gramere and the Old French gramaire, the root of the word is an alteration of the Latin grammatica, which we can trace back to its source from the Greek feminine of grammatikos, meaning “of letters.” It seems appropriate that this feminine derivative from the language of one of the earliest classical pantheistic civilizations has evolved to describe what is now considered by many witches to be a sacred text devoted to rituals honoring the Mother Goddess. Most of the books that are now commonly classified as grimoires, however, were written during the Middle Ages and the Renaissance. They speak of many different traditions of ceremonial magic, both sacred and profane.

Most often, today's grimoire is handwritten by individuals for their own personal use. In a grimoire, there may be specific instructions that pertain to a particular tradition, or it may contain strictly personal records intended only for the use of the individual author. Sometimes the grimoire (or sections of it) is passed down or copied from a master book. The term grimoire is generic and may be used in place of the title of the actual book, which is often kept secret. What is popularly known as the “book of shadows” is really a sort of Wiccan recipe book that includes spells and incantations, but also much more. A book of shadows may also contain dreams, poems, invocations, revelations, inspiration, and lore.
Every grimoire is essentially a book of shadows, but not every book of shadows would conform to the definition of a grimoire. A book of shadows differs from a grimoire in that while it includes elements of the grimoire, it is not necessarily an exclusively instructive tome, but more of a personal record of a spiritual journey.
Some people argue that a book of shadows more closely resembles a diary or a journal and that highly personal musings have no place in the more didactic grimoire. Purists insist that the grimoire should be entirely instructional, full of information, annotation, and practical application. Fortunately for our purposes, there exists no officially designated criterion for creating a book of shadows, nor is there a correct or incorrect way of building, blessing, and usingh your personal grimoire.